This invention relates to a device for grinding materials in a liquid and pumping the same from a basin. More particularly, this invention relates to a device which will efficiently grind large materials into a fine slurry without clogging through a unique pumping and comminutor arrangement.
In the prior art of which we are aware, material to be ground and disposed of is entrained in a liquid and drawn axially into a pump chamber through a comminutor. The motive force for the pumping action is typically an impeller mounted in the pump chamber which centrifugally throws the ground material and liquid through a radial discharge. However, with the impeller situated in the chamber, it often promotes clogging of the material both behind the comminutor and on the impeller itself which tends to bind the same, thus reducing pump efficiency. Such impellers are also often used to provide secondary shearing which too hinders their pumping efficiency. In addition, such a positioned impeller requires close running clearances, thus adding to the cost of precision manufacturing.
The comminutors of the prior art usually consist of a stationary cutting ring positioned in the pump inlet and having cutting teeth or blades on the internal face thereof. An impeller disk having an external diameter generally corresponding to the internal diameter of the ring is rotated within the ring. The disk usually is provided with a plurality of cutting blades with the entire unit being positioned totally within the axial extent of the ring. Ideally, the material is supposed to be cut by the blade and drawn through the small openings between the cutting teeth of the ring and the outer edge of the disk to be further cut by the pump impeller in the pump chamber and subsequently radially discharged out of the chamber. Unfortunately larger materials, such as large rags, tend to wind around the cutting blades on the disk and/or clog the small passages between the cutting teeth on the ring. The smaller or more fiberous materials, such as disposable diapers, usually will pass through the passages but will tend to wad up behind the impeller disk. Thus, the prior art designs do not efficiently handle all types of materials which may be encountered.
In addition, in these prior art designs with the blades positioned entirely within the axial extent of the cutting ring, grease or other coagulants, when mixed with the solids to be ground, tend to build up on the pumping and cutting surfaces thereby clogging the same. Similarly, hard objects, such as wire, often lodge between the cutting blade and teeth on the ring thereby locking the motor shaft.